The present invention relates to a liquid crystalline compound and a liquid crystal composition. More specifically, it relates to a novel liquid crystalline compound having a negative dielectric anisotropy value (xcex94∈), a liquid crystal composition comprising this compound as one of components and a liquid crystal display device comprising this liquid crystal composition.
In recent years, liquid crystal display devices of various modes have been developed in order to obtain a liquid crystal display having a high quality. In particular, an in-plane switching (IPS) mode and a vertical aligning (VA) mode are paid attentions in developing a liquid crystal display having a wide viewing angle. Liquid crystal compositions used for these liquid crystal display devices are expected to have a negative and absolutely large value of xcex94∈, and hence many developments have been actively made on liquid crystal materials to meet the expectation as above.
Known as such liquid crystal materials having a negative and absolutely large value of xcex94∈ are, for example, 2,3-dicyanophenylene expressed by a formula (13) (Japanese Patent Application Laid-Open No. 10557/1984) and liquid crystalline compounds having a 2,3-difluorophenylene skeleton expressed by formulas (14) or (15) (Japanese Patent Application Laid-Open No. 1725/1990 or Japanese Patent Application WO Laid-Open No. 503441/1990, respectively): 
wherein R and Rxe2x80x2 represent an alkyl group and the like.
However, among these known compounds, 2,3-dicyanophenylene expressed by the formula (13) has a negative and absolutely large value of xcex94∈, but has a problem that it is not only inferior in a compatibility but also lacking in a chemical and physical stability. Accordingly, it is not necessarily satisfactory.
The compound expressed by the formula (14) is simply shown as a component for a ferroelectric liquid crystal composition, and therefore applicability thereof as a nematic liquid crystal composition is not clear. Further, the compound expressed by the formula (15) is shown without any electro-optical characteristics thereof, and therefore it""s applicability as a component for a nematic liquid crystal composition is not clear as well.
An object of the present invention is to solve the defects in conventional technology described above. Another object of the present invention is to provide a novel liquid crystalline compound having a negative and absolutely large xcex94∈ value, being excellent in a compatibility with other liquid crystalline compounds, having a low viscosity, and being stable chemically and physically; to provide a liquid crystal composition comprising the compound as one of components, and to provide a liquid crystal display device comprising the liquid crystal composition.
For achieving the object described above, the present invention is summarized as follows:
(1) A liquid crystalline compound expressed by the general formula (1):
R1xe2x80x94A1xe2x80x94B1xe2x80x94A2xe2x80x94B2xe2x80x94A3xe2x80x94B3xe2x80x94Zxe2x80x94B4xe2x80x94A4xe2x80x94R2xe2x80x83xe2x80x83(1)
wherein A1, A2, A3 and A4 each independently represent a single bond, 1,4-cyclohexylene, 1,4-phenylene which may be substituted with a fluorine atom(s), dioxane-2,5-diyl, pyrimidine-2,5-diyl, piperidine-1,4-diyl, pyridine-2,5-diyl which may be substituted with a fluorine atom(s) or 1-sila-1,4-cyclohexylene; Z represents a group selected from divalent groups expressed by partial structural formulas (I) to (VI): 
wherein X represents a hydrogen atom or a fluorine atom, and Y represents difluoromethyl group, difluoromethoxy group, formyl group or carboxyl group; B1, B2, B3 and B4 each independently represent a single bond, 1,2-ethylene, 1,2-ethenylene, 1,2-ethynylene, oxymethylene, methyleneoxy, carbonyloxy, oxycarbonyl or 1,4-butylene group, provided that when Z is a group represented by the partial structural formula (III), then B4 is neither oxymethylene nor oxycarbonyl group, and that when Z is a group represented by the partial structural formula (IV), then B3 is neither methyleneoxy nor carbonyloxy group; R1 and R2 each independently represent an alkyl group or a fluoroalkyl group substituted with at least one fluorine atom having 1 to 10 carbon atoms in which alkyl group or fluoroalkyl group one or not adjacent two or more methylene groups may be replaced by an oxygen atom, a sulfur atom or xe2x80x94CHxe2x95x90CHxe2x80x94.
(2) The liquid crystalline compound as recited in paragraph 1 wherein Z is a group represented by the partial structural formula (I).
(3) The liquid crystalline compound as recited in paragraph 1 wherein Z is a group represented by the partial structural formula (II).
(4) The liquid crystalline compound as recited in paragraph 1 wherein Z is a group represented by the partial structural formula (V).
(5) The liquid crystalline compound as recited in paragraph 1 wherein Z is a group represented by the partial structural formula (VI).
(6) A liquid crystal composition comprising two or more components at least one of which is a liquid crystalline compound recited in any of paragraphs 1 to 5 above.
(7) A liquid crystal composition comprising, as a first component, at least one liquid crystalline compound recited in any one of paragraphs 1 to 5 above, and, as a second component, at least one compound selected from the group consisting of the compounds expressed by any one of the formulas (2), (3) and (4): 
wherein R3 represents an alkyl group having 1 to 10 carbon atoms in which alkyl group one or not adjacent two or more methylene groups may be replaced by an oxygen atom or xe2x80x94CHxe2x95x90CHxe2x80x94, and any hydrogen atom thereof may be replaced by a fluorine atom; Y1 represents a fluorine atom, a chlorine atom, OCF3, OCF2H, CF3, CF2H, CFH2, OCF2CF2H or OCF2CFHCF3; L1 and L2 each independently represent a hydrogen atom or a fluorine atom; Z1 and Z2 each independently represent a 1,2-ethylene group, a 1,4-butylene group, xe2x80x94COOxe2x80x94, xe2x80x94CF2Oxe2x80x94, xe2x80x94OCF2xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94 or a single bond; ring B represents trans-1,4-cyclohexylene, 1,3-dioxane-2,5-diyl or 1,4-phenylene in which any hydrogen atom on the ring may be replaced by a fluorine atom; and ring C represents trans-1,4-cyclohexylene, or 1,4-phenylene in which any hydrogen atom on the ring may be replaced by a fluorine atom.
(8) A liquid crystal composition comprising, as a first component, at least one liquid crystalline compound recited in any one of paragraphs 1 to 5 above, and, as a second component, at least one compound selected from the group consisting of compounds expressed by the formulas (5) and (6): 
wherein R4 and R5 each independently represent an alkyl group having 1 to 10 carbon atoms in which alkyl group one or not adjacent two or more methylene groups may be replaced by an oxygen atom or xe2x80x94CHxe2x95x90CHxe2x80x94, and any hydrogen atom thereof may be replaced by a fluorine atom; Y2 represents a xe2x80x94CN group or xe2x80x94Cxe2x89xa1Cxe2x80x94CN; ring E represents trans-1,4-cyclohexylene, 1,4-phenylene, 1,3-dioxane-2,5-diyl or pyrimidine-2,5-diyl; ring G represents trans-1,4-cyclohexylene, 1,4-phenylene 4-phenylene in which any hydrogen atom on the ring may be replaced by a fluorine atom or pyrimidine-2,5-diyl; ring H represents trans-1,4-cyclohexylene or 1,4-phenylene; Z3 represents a 1,2-ethylene group, xe2x80x94COOxe2x80x94 or a single bond; L3, L4and L5each independently represent a hydrogen atom or a fluorine atom; and b, c and d each independently represent 0 or 1.
(9) A liquid crystal composition comprising, as a first component, at least one liquid crystalline compound recited in any one of paragraphs 1 to 5 above, and as a second component, at least one compound selected from the group consisting of the compounds expressed by any one of the formulas (7), (8) and (9): 
wherein R6 and R7 each independently represent an alkyl group having 1 to 10 carbon atoms in which alkyl group one or not adjacent two or more methylene groups may be replaced by an oxygen atom or xe2x80x94CHxe2x95x90CHxe2x80x94, and any hydrogen atom thereof may be replaced by a fluorine atom; rings I, J and K each independently represent trans-1,4-cyclohexylcne, pyrimidine-2,5-diyl or 1,4-phenylene in which any hydrogen atom on the ring may be replaced by a fluorine atom; and Z4 and Z5 each independently represent xe2x80x94Cxe2x89xa1Cxe2x80x94, xe2x80x94COOxe2x80x94, xe2x80x94CH2CH2xe2x80x94, xe2x80x94CHxe2x95x90CHxe2x80x94 or a single bond.
(10) A liquid crystal composition comprising, as a first component, at least one liquid crystalline compound recited in any one of paragraphs 1 to 5 above, as a second component, at least one compound selected from the group consisting of the compounds expressed by any one of the formulas (2), (3) and (4) described above, and, as a third component, at least one compound selected from the group consisting of the compounds expressed by any one of the formulas (7), (8) and (9) described above.
(11) A liquid crystal composition comprising, as a first component, at least one liquid crystalline compound recited in any one of paragraphs 1 to 5 above, as a second component, at least one compound selected from the group consisting of the compounds expressed by any one of the formulas (10), (11) and (12): 
wherein R8 and R9 each independently represent an alkyl group having 1 to 10 carbon atoms in which alkyl group one or not adjacent two or more methylene groups may be replaced by an oxygen atom or xe2x80x94CHxe2x95x90CHxe2x80x94, and any hydrogen atom thereof may be replaced by a fluorine atom; rings L and M each independently represent trans-1,4-cyclohexylene or 1,4-phenylene; L6 and L7 each independently represent a hydrogen atom or a fluorine atom but never be hydrogen atoms at the same time; and Z6 and Z7 each independently represent xe2x80x94CH2CH2xe2x80x94, xe2x80x94CH2Oxe2x80x94 or a single bond.
(12) A liquid crystal composition comprising, as a first component, at least one liquid crystalline compound recited in any one of paragraphs 1 to 5 above, as a second component, at least one compound selected from the group consisting of the compounds expressed by any one of the formulas (7), (8) and (9) described above, and, as a third component, at least one compound selected from the group consisting of the compounds expressed by any one of the formulas (10), (11) and (12) described above.
(13) A liquid crystal composition comprising, as a first component, at least one liquid crystalline compound recited in any one of paragraphs 1 to 5 above, as a second component, at least one compound selected from the group consisting of compounds expressed by the formulas (5) and (6) described above, and, as a third component, at least one compound selected from the group consisting of the compounds expressed by any one of the formulas (7), (8) and (9) described above.
(14) A liquid crystal composition comprising, as a first component, at least one liquid crystalline compound recited in any one of paragraphs 1 to 5 above, as a second component, at least one compound selected from the group consisting of the compounds expressed by any one of the formulas (2), (3) and (4) described above, as a third component, at least one compound selected from the group consisting of compounds expressed by the formulas (5) and (6) described above, and, as a fourth component, at least one compound selected from the group consisting of the compounds expressed by any one of the formulas (7), (8) and (9) described above.
(15) A liquid crystal composition recited in any one of paragraphs 6 to 14 wherein the liquid crystal composition further comprises an optically active compound.
(16) A liquid crystal display device comprising the liquid crystal composition as recited in any one of paragraphs 6 to 15.
As described above, the liquid crystalline compound of the present invention is expressed by the general formula (1), and any compounds thereof have such excellent characteristics that they have a negative and absolutely large xcex94∈ value, being excellent in a compatibility with other liquid crystalline compounds, especially at a low temperature, having a low viscosity, and being stable chemically and physically.
Among them, the compounds expressed by one of the following formulas (1-1) to (1-87) can be mentioned as preferable examples thereof. 
wherein X, Y, R1 and R2 have same meaning as described above.
The characteristics of the preferable compound of the present invention described above can be studied in light of Z in the general formula (1).
That is, the compounds expressed by the formulas (1-1) to (1-59) are compounds of a kind in which Z is represented by the partial structural formula (I) or (II). These compounds have a negative and in particular absolutely large xcex94∈ value, and therefore should these compounds be added to a liquid crystal composition for a cell as one of the components, the cell can achieve both reduction of threshold voltage and increase of response speed.
The compounds expressed by the formulas (1-60) to (1-71) are compounds of a kind in which Z is represented by the partial structural formula (III) or (IV). These compounds have a negative and relatively large absolute xcex94∈ value and a low viscosity, and therefore should these compounds be added to a liquid crystal composition for a cell as one of the components, the cell can achieve increase of response speed.
The compounds expressed by the formulas (1-72) to (1-87) are compounds of a kind in which Z is represented by the partial structural formula (V) or (VI). These compounds have a negative and absolutely large xcex94∈ value and a large optical anisotropy value (xcex94n), and therefore should these compounds be added to a liquid crystal composition for a cell as one of the components, the cell can not only reduce threshold voltage of the cell but also can control the xcex94n.
Further, these compounds exhibit a wide temperature range of liquid crystal phase and therefore are useful for the purpose of widening temperature range of a liquid crystal composition for the cell.
In the liquid crystalline compound of the present invention expressed by the general formula (1), A1, A2, A3 and A4 each independently represent, as already described, a single bond, a 1,4-cyclohexylene, 1,4-phenylene which may be substituted with a fluorine atom(s), dioxane-2,5-diyl, pyrimidine-2,5-diyl, piperidine-1,4-diyl, piperidine-2,5-diyl which may be substituted with a fluorine atom(s) or 1-sila-1,4-cyclohexylene ring. While the single bond may preferably be selected in the numeral range of 1 to 4, this leads that ring groups out of A1, A2, A3 and A4 are in the numeral range of zero to three.
B1, B2, B3 and B4 each independently represent, as already described, a single bond, 1,2-ethylene, 1,2-ethenylene, 1,2-ethynylene, oxymethylene, methyleneoxy, carbonyloxy, oxycarbonyl or 1,4 -butylene group, provided that when Z is a group represented by the partial structural formula (III), then B4 is preferably neither oxymethylene nor oxycarbonyl group, and that when Z is a group represented by the partial structural formula (IV), then B3 is preferably neither methyleneoxy nor carbonyloxy group.
R1 and R2 each represent those, which have already been described, and as their preferred examples, followings can be mentioned.
Alkyl group such asmethyl, ethyl, propyl, butyl, pentyl, hexyl or heptyl; alkoxy group such as methoxy, ethoxy, propoxy, butoxy, pentyloxy or heptoxy; alkoxyalkyl group such as methoxymethyl; alkenyl group such as vinyl, allyl, 1-propenyl, 3-butenyl, 4-pentenyl, trans-3-pentenyl or 5-hexenyl; fluoroalkyl group substituted with at least one fluorine atom such as difluoromethyl, trifluoromethyl, pentafluoroethyl or heptafluoromethyl; fluoroalkoxy group substituted with at least one fluorine atom such as difluoromethoxy, trifluoromethoxy, 2,2,2-trifluoroethoxy, 2,2,3,3,3-pentafluoropropoxy or 1,1,2,3,3,3-hexafluoropropoxy; fluoroalkenyloxy group substituted with at least one fluorine atom such as 3,3-difluoro-2-propenyloxy or 1,1-difluoro-2-propenyloxy; or alkylthio group such as ethylthio or butylthio.
Whereas a large part of the liquid crystalline compounds of the present invention expressed by the general formula (1) exhibit a liquid crystal phase, there are some that exhibit no liquid crystal phase. However, even such liquid crystalline compounds as exhibiting no liquid crystal phase, these are useful as components for a liquid crystal composition, since the compounds have a good compatibility with other liquid crystalline compounds, as is the case with those exhibiting a liquid crystal phase, and further, the compounds do not markedly reduce or retrench the nematic phase temperature range thereof when they are mixed with other liquid crystalline compounds.
The liquid crystal composition of the present invention comprises, as a first component, at least one liquid crystalline compound expressed by the general formula (1).
Its content is preferably to be in the range of 0.1 to 99.9% by weight based on the weight of the liquid crystal composition for developing excellent characteristics.
While the liquid crystal composition of the present invention may comprise only the first component described above, the compositions in which at least one compound selected from the group consisting of the compounds expressed by any one of the formulas (2), (3) and (4) (hereinafter referred to as second component A), at least one compound selected from the group consisting of compounds expressed by the formulas (5) and (6) (hereinafter referred to as a second component B), at least one compound selected from the group consisting of the compounds expressed by any one of the formulas (7), (8) and (9) described above (hereinafter referred to as a third component A) or at least one compound selected from the group consisting of the compounds expressed by any one of the formulas (10), (11) and (12) (hereinafter referred to as a third component B) are preferably mixed alone or in combination thereof. Besides, an optically active compound as another component, and a known compounds may be mixed for the purpose of adjusting the threshold voltage, the temperature range of liquid crystal phase, xcex94n, xcex94∈ or viscosity.
Among the second component A described above, the compounds expressed by one of the following formulas (2-1) to (2-9) can be mentioned as suitable examples of the ones included in the formula (2), the compounds expressed by one of the following formulas (3-1) to (3-69) can be mentioned as suitable examples of the ones included in the formula (3), and the compounds expressed by one of the following formulas (4-1) to (4-24) can be mentioned as suitable examples of the ones included in the formula (4), respectively. 
wherein R3 and Y1 have the same meaning as described above.
All of the compounds expressed by one of the formulas (2) to (4) exhibit a positive xcex94∈ (P type compounds), are very excellent in thermal stability and chemical stability, and are indispensable when a liquid crystal composition for TFT (AM-LCD) of which a high reliability such as a high voltage-holding ratio (large specific resistance) is required are produced.
While the amount of the compound to be used is suitably in the range of 1 to 99.9% by weight based on the total amount of the liquid crystal composition when liquid crystal composition for TFT are produced, it is preferably 10 to 97% by weight and more desirably 40 to 97% by weight. In this case, liquid crystal compositions may further comprise a compound expressed by one of the formulas (7) to (9) for the purpose of adjusting viscosity.
While the compounds expressed by one of the formulas (2) to (4) described above can be used when liquid crystal compositions for STN display mode or TN display mode are produced, the amount of the compound to be used is preferably less than 50% by weight based on the total amount of liquid crystal composition since this compound is small in its effect of lowering threshold voltage of liquid crystal composition.
Next, among the second component B described above, the compounds of one of the formulas (5-1) to (5-40) can be mentioned as preferable examples of the ones included in formula (5), and the compounds of one of the formulas (6-1) to (6-3) can be mentioned as preferable examples of the ones included in formula (6), respectively. 
wherein R41 R5 and Y2 have the same meaning as described above.
Any compounds expressed by formulas (5) or (6) have a positive and large xcex94∈ value, and are used particularly for the purpose of lowering threshold voltage of liquid crystal compositions.
Also, the compounds are used for the purpose of adjusting xcex94n or widening temperature range of nematic phase by raising clearing point of liquid crystal compositions, and also for the purpose of improving the steepness of liquid crystal compositions for STN display mode or TN display mode, and thus are indispensable particularly when liquid crystal compositions for STN display mode or TN display mode are produced.
Whereas the compounds can lower threshold voltage of the liquid crystal compositions as their amount is increased, the use of the compounds brings about increase of the viscosity.
Accordingly, it is advantageous to use the compounds in a large amount for driving display devices at a low voltage so far as viscosity of liquid crystal compositions satisfies the required characteristics.
From such state of things, the amount of the compounds to be used is suitably in the range of 0.1 to 99.9% by weight, preferably 10 to 97% by weight, and more desirably 40 to 97% by weight based on the total amount of liquid crystal composition when liquid crystal composition for STN display mode or TN display mode are produced.
Among the third component A described above, the compounds of one of the formulas (7-1) to (7-11) can be mentioned as preferable examples of the ones included in formula (7), the compounds of one of the formulas (8-1) to (8-18) can be mentioned as preferable examples of the ones included in formula (8), and the compounds of one of the formulas (9-1) to (9-6) can be mentioned as preferable examples of the ones included in formula (9). 
wherein R6 and R7 have the same meaning as described above.
Any compounds expressed by one of formulas (7) to (9) have a small absolute value of xcex94∈. Among them, the compounds of the formula (7) are used principally for the purpose of adjusting viscosity or adjusting xcex94n of liquid crystal compositions, and the compounds of the formula (8) or (9) are used for the purpose of widening nematic range and adjusting xcex94n.
Whereas these compounds raise threshold voltage of liquid crystal compositions as their amount used is increased, the use of the compounds reduces the viscosity. Accordingly, it is desirable to use compounds in a larger amount so far as the threshold voltage of liquid crystal composition satisfies required value.
From such state of things, the amount of the compounds to be used is suitably 40% by weight or less and preferably 35% by weight or less based on the total amount of liquid crystal composition when liquid crystal compositions for TFT are produced.
On the other hand, when liquid crystal compositions for STN display mode or TN display mode are produced, the amount of use described above is 70% by weight or less, preferably 60% by weight or less based on the total amount of the liquid crystal composition.
Among the third component B described above, the compounds of one of the formulas (10-1) to (10-3) can be mentioned as preferable examples of the ones included in formula (10), the compounds of one of the formulas (11-1) to (11-5) can be mentioned as preferable examples of the ones included in formula (11), and the compounds of one of the formulas (12-1) to (12-3) can be mentioned as preferable examples of the ones included in formula (12). 
wherein R8 and R9 have the same meaning as described above.
Any compounds expressed by one of formulas (10) to (12) have a negative xcex94∈ (N type compounds).
The two-rings system compounds expressed by the formula (10) are used principally for the purpose of adjusting threshold voltage, viscosity or xcex94n of liquid crystal compositions, and the compounds expressed by the formula (12) are used for the purpose of widening nematic range, lowering threshold voltage or enlarging absolute value of xcex94∈ in negative.
The compounds expressed by the formula (10) to (12) are used mainly as an N type compounds. Whereas these compounds lower threshold voltage while increase viscosity of liquid crystal compositions as their amount used is increased, it is desirable to use the compounds in a smaller amount so far as the threshold voltage of liquid crystal composition satisfies required value.
However, the compounds are disadvantageous for driving at a low voltage due to their smaller absolute value of xcex94∈ as 5 or less, and therefore the amount to be used has to be settled in an effective level or more.
For example, the amount of the compounds to be used described above is suitably 40% by weight or more and preferably 50 to 95% by weight when liquid crystal compositions for TFT of N type are produced.
Further, the amount described above is preferably 30% by weight or less when liquid crystal compositions are produced by adding the compounds to a P type liquid crystal, for the purpose of controlling an elastic constant and a voltage-transmittance curve (V-T curve).
The compounds expressed by the formulas (1) to (12) explained above may be those in which a certain proportion of atoms constituting the molecules are replaced by their isotopes.
The reason is that even the compounds thus replaced by isotopes are found to have no difference from the non-replaced compounds in view of liquid crystal characteristics.
Among other components described above, an optically active compound is usually added for the purpose of inducing helical structure of liquid crystal compositions to adjust required twist angle and to prevent reverse twist, with the exception of specific cases, for instance, the case of liquid crystal compositions for OCB (Optically Compensated Birefringence) mode.
While the optically active compound is widely selected from known compounds so far as the purpose described above can be achieved, the optically active compounds expressed by one of the following formulas (Op-1) to (Op-8) can preferably be mentioned. 
Pitch length of the twist in liquid crystal compositions is adjusted by adding these optically active compounds. The twist pitch length is preferably adjusted in the range of 40 to 200 xcexcm in the case of liquid crystal compositions for TFT or TN, preferably adjusted in the range of 60 to 20 xcexcm in the case of the compositions for STN, and preferably adjusted in the range of 1.5 to 4 xcexcm in the case of the compositions for bistable TN mode, respectively. In such cases, two or more kinds of optically active compounds may be added for the purpose of adjusting the dependency of pitch length on temperature.
Liquid crystal compositions of the present invention can be produced by methods, which are conventional. For instance, the compositions are produced by a method in which various components are dissolved in one another at a high temperature.
Further, the compositions can be used as ones for guest-host (GH) mode by adding a dichroic dye such as merocyanine type, styryl type, azo type, azomethine type, azoxy type, quinophthalone type, anthraquinone type, or tetrazine type thereto. Alternatively, the liquid crystal compositions can be used as NCAP which is prepared by microencapsulation of a nematic liquid crystal, or as liquid crystal compositions for polymer dispersed liquid crystal display devices (PDLCD) represented by polymer network liquid crystal display devices (PNLCD) prepared by forming a polymer of three-dimensional reticulated structure in a liquid crystal.
Still further, the liquid crystal compositions can be used as ones for electrically controlled birefringence (ECB) mode or dynamic scattering (DS) mode.
The liquid crystal compositions of the present invention are produced in such a manner as described above, and examples thereof (Composition Examples) are shown below.
In each of the Composition examples, compounds used as the components are shown s by referring to the definitions given in Table 1. Compound No. appended to the compounds means that the compounds are the same as those shown in Examples described later, and the content of compounds means % by weight unless otherwise specified.
Further, data of characteristics of compositions in Composition Examples are indicated by NI (phase transition temperature of nematic-isotropic liquid, or clearing point), xcex7 (viscosity: determined at 20xc2x0 C.), xcex94n (optical anisotropy value: determined at 25xc2x0 C.) and Vth (threshold voltage: determined at 25xc2x0C.).
[Table 1]
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Characteristics of this composition were determined to be as follows:
NI=73.8(xc2x0C.)
xcex7=25.9(mPaxc2x7s)
xcex94n=0.087
xcex94∈=xe2x88x921.9
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Characteristics of this composition were determined to be as follows:
NI=83.3(xc2x0C.)
xcex94n=0.080
xcex94∈=xe2x88x923.8
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Characteristics of this composition were determined to be as follows:
NI=87.4(xc2x0C.)
xcex94n=0.079
xcex94n=xe2x88x923.4
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Characteristics of this composition were determined to be as follows:
NI=78.8(xc2x0C.)
xcex94n=0.150
xcex94∈=xe2x88x923.1
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Characteristics of this composition were determined to be as follows:
NI=85.6(xc2x0C.)
xcex7=18.7(mPaxc2x7s)
xcex94n=0.158
xcex94∈=6.8
Vth=2.13(V)
Optically active compound expressed by the formula (Op-4) described above in an amount of 0.8 part by weight was mixed to 100 parts by weight of the primary composition described just above to obtain a secondary composition, and the secondary composition was determined to have pitch of 10.5 xcexcm.
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Characteristics of this composition were determined to be as follows:
NI=84.2(xc2x0C.)
xcex7=18.1(mPaxc2x7s)
xcex94n=0.114
xcex94∈=4.5
Vth=2.41(V)
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Characteristics of this composition were determined to be as follows:
NI=87.1(xc2x0C.)
xcex7=24.6(mPaxc2x7s)
xcex94n=0.125
xcex94∈=4.4
Vth=2.42(V)
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Characteristics of this composition were determined to be as follows:
NI=74.0(xc2x0C.)
xcex7=36.1(mPaxc2x7s)
xcex94n=0.083
xcex94∈=12.8
Vth 1.48(V)
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Liquid crystal composition comprising the following components in the amount shown below was prepared:
Compounds of the present invention expressed by the general formula (1) can be prepared by such a known method of ordinary organic synthesis as following.
(A) Production of compounds expressed by the general formula (1) in which Z is represented by the partial structural formula (I), (II), (III) or (IV): 
wherein X has the same meaning as described above; m and n each independently are 0 or 1 with proviso that m+n is 1; Q1 and Q2 each independently represent R1-A1-B1-A2-B2-A3-B3 or R2-A4-B4 with proviso that Q1xe2x89xa0Q2.
The compound expressed by a formula (a-1) is reacted with n-BuLi or sec-BuLi to obtain a lithiation compound (a-2), and this compound is then reacted with DMF or N-formylpiperidine or the like to obtain the compound example of the present invention (1) in which Y in the partial structural formula described above is formyl.
Thus obtained compound is oxidized with a Jone""s reagent or the like or fluorinated with diethylaminosulfur trifluoride (DAST) or the like to obtain the compound example of the present invention (1) in which Y in the partial structural formula described above is carboxyl (see eq. a) or Y is difluoromethyl (cf. eq. b).
Further, the compound (a-2) is subjected to hydroxylation via boric acid, and then reacted with chlorodifluoromethane or the like to obtain the compound example of the present invention (1) in which Y is difluoromethoxy (cf. eq. c).
Still further, the compound expressed by the formula (a-1) described above which is a starting material can readily be synthesized by such a method as following.
That is, the compound in which Z is given as either the partial structural formula (I) or (III) and X is a fluorine atom can be synthesized according to the known method, such as the one described in Liq. Cryst., 21, 279 (1996), by brominating 3-fluorophenol to obtain the compound (d-1), then reacting it with an appropriate bromomethyl derivative to obtain the compound (d-2) and then subjecting this compound to several known reaction steps (cf. eq. d).
Similarly, the compound as above in which X is a hydrogen atom can be synthesized in the same manner as described above, except that 4-bromoanisole is used in place of the compound (d-1).
The compound in which Z is given as either the partial structural formula (II) or (IV) and X is a fluorine atom can be synthesized by reacting 4-boromo-3-fluorotoluene with NBS (N-bromosuccinimide) or the like to brominate the former""s methyl group, followed by reacting thus obtained compound with an appropriate hydroxymethyl derivative and then followed by subjecting thus obtained compound to several known reaction steps (cf. eq. e). Similarly, the compound as above in which X is a hydrogen atom can be synthesized in the same manner as described above, except that 4-bromotoluene is used in place of 4-boromo-3-fluorotoluene.
(B) Production of compounds expressed by the general formula (1) in which Z is represented by the partial structural formula (V) or (VI): 
wherein Q1 and Q2 have the same meaning as described above.
The compound expressed by a formula (f-1) is reacted with n-BuLi or sec-BuLi to obtain a lithiation compound (f-2), and followed by a reaction in the same manner as in the cases of (eq. a), (eq. b) or (eq. c), except that the lithiation compound (f-2) thus obtained is used in place of the lithiation compound (a-2) (cf. eq. f).
Still further, the compound expressed by the formula (f-1) described above which is a starting material can readily be synthesized by such methods as followings.
That is, a suitable piperidine derivative is subjected to a coupling reaction with 4-bromoiodobenzene according to the method described in J. Org. Chem., 62, 6066 (1997) or the like to convert it to a compound (g-1), followed by a reaction in which a bromine atom of this compound is converted to various substituents along with the objects of the present invention (cf eq. g), or a suitable piperidine derivative is subjected to a coupling reaction with 4-chloro-3-fluorobromobenzene according to the method described in J. Am. Chem. Soc., 118, 7215 (1996) to convert it to a compound (h-1), followed by a reaction in which a chlorine atom of thus obtained compound is converted to an iodine atom according to the method described in J. Org. Chem., 23, 305 (1958) to obtain a compound (h-2), followed further by a reaction in which the iodine atom is converted to various substituents along with the objects of the present invention (cf. eq. h).
The compound example of the present invention (1) thus obtained can readily be isolated by subjecting the reaction solution obtained after the reaction is finished to a conventional extraction treatment, and further by carrying out refining operations such as distillation, recrystallization or column chromatography or the like.